Chapter 2

Translated from Chinese by an LLM.

Memory

An array occupies contiguous space; each access reads base address + index, so the complexity is $O(1)$ .
A linked list occupies non-contiguous space; each access follows the next address, so the complexity is $O(n)$ .
Comparison table for insert, delete, update, and query:

Operation	Array	Linked List
Insert	$O(n)$	$O(1)$
Delete	$O(n)$	$O(1)$
Update	$O(1)$	$O(n)$
Query	$O(1)$	$O(n)$

Selection Sort

Selection sort has the same complexity as bubble sort: $O(n^2)$ . ~~Painfully slow.~~
As shown: svg
The principle is to pick the smallest (or largest) element each time and place it in order until sorted.

Chapter 3 Chapter 1